a. Field of the Invention
This invention relates to a printing or copying apparatus having a control system which is effective to the processing required for printing or copying.
b. Description of the Prior Art
In a copying apparatus having, for example, a drumshaped image formation member, continuous copying could heretofore be accomplished by rotating the drum and at the same time, using drum signals to continuously repeat the processes such as formation of a latent image on the image formation member, development of the latent image and transfer of the developed image. Therefore, in continuous copying, it has been required that the devices necessary for an earlier process be already started to operate before a subsequent process is begun. However, the presence of a device such as paper feed roller which is to be started later has made it unavoidable to secure some interval between a process and a subsequent process and accordingly, the formation of a first latent image could not immediately be followed by the start of the formation of a second latent image. This has led to limitations in increasing the copying speed and in addition, a disadvantage that the shape of the drum cannot efficiently be determined.
Further, many of the conventional copying machines have been such that when a number of copies are to be produced from the same image original, the original is illuminated and scanned to form an electrostatic latent image on a photosensitive medium each time, but this has made it mechanically difficult to reduce the time required for the optical scanning system to return to its original position after the illumination and scanning and therefore, enhancement of the copying speed has been limited. Furthermore, continuous production of multiple copies has required the photosensitive medium to be repetitively used and this has led to great fatigue or wear and accordingly, shorter life, of the photosensitive medium.
Heretofore, setting and counting of the number of copies to be produced and display of the set value or the counted value have been done by a selector using a ratchet-gear combination or by a mechanical selector using rotary switches or thumb wheel switches for respective display digits.
However, the purely mechanical selector is not suited for high-speed copying and the selector using rotary switches or the like has been liable to cause malfunctioning resulting from unsatisfactory engagement between the mechanical contacts thereof and moreover, where a number of digit places are to be set, a correspondingly great number of rotary switches have been required and this has led to great cumbersomeness involved in the setting of the number of copies.
Also, in the conventional copying machines, paper jam occurring within the machine has been indicated by a lamp or the like provided on the panel of the machine and such display has been done independently of other displays (display of the number of copies and the like). Thus, on the panel, various display devices must be discretely provided such as the display device for displaying the number of copies, the display device exclusively for display of jam and other display devices and this involves great complication of the panel structure and the necessity of correspondingly numerous mechanisms and circuits for driving the individual display devices. With the present day tendency of copying machines toward diversification in view, this will further add to complication of the mechanisms and circuits in copying machines. Therefore, if it is desired to display as various states as possible of the machine, the operator or serviceman will have to acquire advanced technical skill regarding the display devices. If, on the other hand, it is desired to reduce the number of display devices the repair or check of a failure in the machine will become difficult.
Also, when paper happens to jam in its path of conveyance, it is usually the case with the operator that he temporally stops the machine for the purpose of removing the jam. In such a case, if the machine is a copying machine, the number of copies to be produced must be reset, otherwise the number of copies as desired could not be obtained even if copying operation was resumed after the removal of the jam.